The IP addresses for requests from NF such as AMF/SMF/PCF are all 127.0.0.1

Q/A
#1

Hello free5gc teams,

When I using tcpdump to generate pcap packets during TestRegistration in test.sh, the IP addresses for requests from NF such as AMF/SMF/PCF are all 127.0.0.1. How can I present the original sbi address of NF.

AMF: sbi address 127.0.0.18
SMF: sbi address 127.0.0.2

2025-10-15T03:11:54.150526596Z [INFO][UDR][GIN] | 200 | 127.0.0.1 | GET | /nudr-dr/v2/subscription-data/imsi-208930000007487/20893/provisioned-data/am-data?supported-features= |
2025-10-15T03:11:54.189411403Z [INFO][UDR][GIN] | 204 | 127.0.0.1 | PUT | /nudr-dr/v2/subscription-data/imsi-208930000007487/context-data/amf-3gpp-access | |
2025-10-15T03:11:54.189602378Z [INFO][UDM][GIN] | 201 | 127.0.0.1 | PUT | /nudm-uecm/v1/imsi-208930000007487/registrations/amf-3gpp-access | |
2025-10-15T03:11:54.263271866Z [INFO][UDR][GIN] | 200 | 127.0.0.1 | GET | /nudr-dr/v2/subscription-data/imsi-208930000007487/context-data/smf-registrations?supported-features= | |
2025-10-15T03:11:54.264304789Z [INFO][UDM][GIN] | 200 | 127.0.0.1 | GET | /nudm-sdm/v2/imsi-208930000007487/ue-context-in-smf-data | |

#2

Hi @fuyong,

For the test configuration is at https://github.com/free5gc/free5gc/blob/0c17c1085029b465e431ceb06d2af9a844c517d6/test/nfs_setup.go.

Actually we have set different local IP for NFs.
I think the reason for only 127.0.0.1 in tcpdump record is that these packets are all transmitted at “lo” network device.

Alonza